"Nonce" eye?

Sleep

Less caffeine or nicotine

I get it too, mostly on days when I've stayed up too late the night before and compensate with coffee.

Does it happen all the time or are there triggers? I find I get a twitch when I'm tired but anxiety or something else could cause it, for example, my eye has just started twitching, so I can probably add the power of suggestion to that list.

If it's permanent, see a doctor.

Most common cause, statistically, is lack of sleep

Try complex vitamin B, shed loads. Stat. And stay away from schools until it clears up